A content delivery network (CDN) is a large distributed system of servers deployed in multiple data centers throughout the Internet. The goal of a CDN is to serve content to end-users with high availability and high performance. Besides better performance and availability, CDNs also offload the traffic served directly from the content provider's origin infrastructure. CDNs can include geographically distributed points of presence (POPs) to locate edge servers close to end users. CDNs are capable of delivering content in high demand with higher quality of service (QoS). Content can be requested from a CDN using a universal resource locator (URL). Various techniques are used to route a URL request to a nearby POP, for example, in order to efficiently retrieve content.